Semiconductor light emitting element formed on a clear or translucent substrate

ABSTRACT

This invention provides a novel application of a semiconductor light emitting element or light emitting chip preferably disposed on the underside surface of a clear or translucent substrate. In addition connecting wires leading from said element to the perimeter of the substrate connecting to contact pads leading to a circuit board. The conductors are deposited on the substrate using thin film technology. Preferably the light emitting element is packaged in a flip chip having connecting bumps only on one side.

BACKGROUND OF THE INVENTION

A. Field of Invention

The present invention relates generally to electronic devices andspecifically to a semiconductor light emitting element formed andpositioned on the surface of a clear or translucent substrate providinga more efficient and even distribution of lighting and thereforeimproving the viewing of an item or object at night or in low lightconditions. The substrate may form or be a part of protective shield,lens or cover of an object being illuminated.

B. Description of the Prior Art

Illumination is widely used in the electronic industry on productsranging from cellular telephones, calculators, watches, hand-heldcomputers, global positioning units and gauges. Illuminating devices arealso used in many other industries such as in automobiles, signs,advertising and ornamentation.

Light emitting diodes have many advantages over competing lightingelements such as electroluminescent, phosphorescent, flourescentelements as well as LCD and incandescent elements in areas such as size,cost, color variables, reliability, and power consumption.

Semiconductor light emitting diodes have been used in cellular phones,watches and other electronics but their illumination has been limiteddue to their positioning underneath, embedment inside a crystal or fromthe side of the light transmissive item receiving the illumination asdescribed in U.S. Pat. No., 6,017,127-Timex, U.S. Pat. No.3,899,871-Seiko, U.S. Pat. No. 4,115,994-Tomlinson.

Electroluminescent lighting, hereinafter referred to as EL, has been inwidespread use in the electronic industry and is usually positionedunderneath the item or object such as watch dials or other surfaces asdescribed in U.S. Pat. No., 3,749,977-Sliker, U.S. Pat. No.4,775,964-Timex, U.S. Pat. No. 4,208,869-Hanaoka. In these referencesthe direct illumination is provided upward towards the viewerrestricting any aesthetic aspects. Another disadvantage of EL's is thatthey require complicated auxiliary circuitry and limited colors to theconsumer market.

OBJECTIVES AND SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present invention to provide animproved and efficient illumination apparatus for viewing an item orobject by positioning an illumination device to direct light in adirection towards the subject to be illuminated making viewing easier,more efficient and less stressful to the viewer.

A further objective of this invention is to remove the semiconductorlight emitting diode packaging including the reflective directional coneand the surrounding glass or plastic protective barrier, thereforeleaving the light emitting element in its raw form which when applied tothe undersurface of the clear or translucent substrate radiates in a180-degree angle and when in off mode leaves the lighting apparatusvirtually invisible.

It is another objective of the present invention to provide anillumination device for electronic devices such as: cellular phones,watches, hand-held computers, global positioning units, gauges,automobiles, signs, advertising and ornamental devices eliminating anyEL as the primary illumination source and its associated circuitry.

Another objective is to group semiconductor light emitting diode chipswhich could be red, green and blue configuration centrally or inselected areas of the substrate regulated independently by a circuit orASICS chip with resistors limiting electrical current providing anunlimited spectrum of colors.

Another objective is to allow constant or preprogrammed illuminationvariables, which could be activated from a power source with apreprogrammed electronic circuit or a programmable ASICS chip and iscontrolled by an actuator switch, which could be within close proximityof the item or object.

These and other objects of the invention, together with features andadvantages thereof will become apparent from the following detaileddescription of the preferred embodiment, the appended claims and theaccompanying drawings.

An illuminating device is disclosed which is formed of a substrate madeof a transparent, translucent or opaque. A plurality of conductors areformed on the substrate using thin film deposition techniques. Theconductors may include several coextensive layers, including a layer ofchromium, a layer of nicker and a layer of gold. A protective layer isthen applied to cover and protect the conductors.

The device further includes one or more light emitting elements, eachelement being formed of semiconductor materials forming a semiconductorjunctions. Importantly, no lenses are provided to concentrate light fromthese elements thereby insuring the light is evenly distributed as itpropagates away from the device. Preferrably the light emitting elementor elements are packaged in a flip chip having connecting bumps on oneside. Therefore the chip can be directly connected to the conductors.

The device may be formed with several light emitting elements arrangedinto multicolored groups. Each group includes a red, a green and a blueelement. The groups can then be activated to form a static or movingcolored image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plan view of an illumination device constructed inaccordance with this invention;

FIG. 2 shows a sectional view of the device of FIG. 1;

FIG. 3 shows an enlarged sectional. view of the illumination device withdetails of the conductors;

FIG. 4 shows a sectional view of a watch incorporating the subjectillumination device;

FIG. 5 is an enlarged sectional view of the watch of FIG. 4; and

FIG. 6 shows a substrate with multi-colored light emitting elements.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2 shows an illumination device constructed in accordancewith this invention. The device 10 includes a substrate 12 which in oneembodiment of the invention is made of a transparent or translucentmaterial such as a glass, quartz or crystal. The substrate 12 can have acircular shape, as shown in FIG. 1, a rectangular, a square shape, orany other regular or irregular shape desired. Two conductors 14, 16 areformed on the substrate 12 using semiconductor techniques, as describedin more detail below. The conductors 14, 16 extend from two connectors18A, 18B preferably disposed near an edge of the substrate 12. The otherends of the conductors 14, 16 consist of bonding pads 20A, 20B,respectively. A light emitting element 22 is secured to the pads 20A,20B (in FIG. 1, element 22 is shown in phantom lines). Preferably theelement 22 is provided in form of a flip chip which has connecting bumps(not shown) on only one surface 22A. Flip chips and methods of attachingthe same to a substrate are disclosed for example in U.S. Pat. No.5,869,886 (incorporated herein by reference). Therefore the element 22can be mounted on substrate 12 solidly and without any connectors orleads required from its top surface 22A. The element 22 is oriented sowhen it is energized by current from conductors 14 and 16, it generateslight, as indicated symbolically in FIG. 2 by rays R. Alternatively,instead of a flip chip, element 22 may be a light emitting element withone connection on each of the surfaces 22A and 22B as shown in commonlyassigned U.S. Pat. No. 6,106,127 incorporated herein by reference. Lightemitting elements of these kinds are available in a variety of colorsfrom Agilent Technologies, a subsidiary of the Hewlett Packard Company,and Sharp Corporation of Japan.

Light emitting diodes are semiconductor devices that are readilyavailable in a large variety of sizes, power output color,configuration, etc. A typical light emitting diode consists of a lightemitting element and a lens. The light emitting element is made of twosemiconductor materials forming a junction so that when a current flowsacross the junction, light is generated. This light is then interceptedby the lens and directed in a predetermined direction. To the inventor'sknowledge, no illuminating devices are presently available which utilizeonly the light emitting element without a lens. However, the inventorhas discovered that the light emitting element of diodes can be usedeffectively without any lens and in that how the element 22 ispreferably used. An illuminating device, such as 10, having thisconfiguration, i.e., one that utilizes a light emitting element withouta lens, has several advantages: first it can illuminate an object moreevenly and across a greater surface area. Second, light emitting elementand its conductors can be made so small that they will be substantiallyinvisible and hence provide an interesting and attractive estheticaspect to any object thus illuminated.

The conductors 14 and 16 are formed on substrate 12 using standard thinfilm technology well known in the art. For example, the conductors maybe formed by the following sequence:

a. a photoresist material is applied to the substrate 12 using, forexample, a spin coater;

b. the substrate is baked for a duration sufficient to cure thephotoresist (for example, 30 minutes);

c. An aligner is used to place a negative mask on the photoresist, themask forming a with a pattern corresponding to the shape of theconductors;

d. the mask is exposed to UV light;

e. The substrate is soaked in a photoresist developer to remove theexposed photoresist;

f. The substrate is loaded in a plasma asher to be cleaned with oxygen;

g. The substrate is placed in a vacuum chamber;

h. Metal is deposited on the substrate using electrode beam evaporation;

i. The substrate is allowed to cool and is removed from the vacuumchamber;

j. The substrate is soaked in acetone to remove the residualphotoresist.

Preferably, this process is performed on a large sheet of substrate sothat several illuminating devices are made at the same time, disposedfor example in a two dimensional array. After step (j) the final productmay be inspected and then cut to the desired size and shape.

The conductors may be formed integrally on the substrate using theprocess outlined above or other similar processes and can be made fromgold, silver, copper, nickel as well as various alloys having arelatively low electrical resistivity. Moreover, it has been found thatinstead of using a single metal layer for forming the conductors,multiple layers may be used. For example, in step (h) three differentlayers may be deposited, as shown in FIG. 3: a layer of chromium Crwhich adheres well to the glass substrate 12, a layer of nickel Ni whichcan be soldered easily; and a layer of gold Au which has a very smallelectrical resistance. Finally, a non-conductive resin may be added ontop of the gold layer to protect the conductors during handling.

The first, or adhesive layer may also be made of titanium or a titaniumtungsten alloy. The second layer may also be made of platinum orpaladium. The third layer may also be made of silver, copper and otheralloys. The second and third layers may be interchanged.

Alternatively, conductors 14, 16 may be made of a transparent ortranslucent material such as Indium Tin Oxide (ITO).

FIGS. 4 and 5 shows a cross-sectional view of a watch 30 and itillustrates how the subject invention may be used. The watch 30 includesa case 32, a dial 34 with indicia 36. A shaft 38 is used to turn twohands 40, 42 in the conventional manner. Disposed on top of the hands40, 42 is the substrate 12 with the conductors 14, 16 and light emittingelement 22 oriented downwardly so as to illuminate the dial 34 and thehands 40, 42.

As seen more clearly in FIG. 5, disposed under the dial 34 there isprovided an IC chip 44 which provides the logic for the movement of thehands 40, 42 and/or the light emitting element 22. The chip 44 isconnected to conductors 14, 16 by a coupling 46.

It should be understood that substrate 12 may be too fragile to protectthe watch 30 adequately and therefore additional protective crystals orother transparent sheets (not shown) may be used to reinforce thesubstrate 12 as well.

In an alternate embodiment of the invention, the dial 34 can beilluminated from the bottom instead of, or as well as, the top. In thisembodiment, the dial 34 may be made of a transparent or translucentmaterial and an illuminating device 12A is positioned under the dial 32,essentially similar to the device 12. In this configuration, the lightemitting element of the device 12A (not shown) is oriented upward sothat its light penetrates through the dial 32. Advantageously, device12A can be made as a discrete element, or it can be integral with thechip 44 or dial 34.

The subject device illustrated in FIGS. 1-3 has been described as beingused to illuminate a watch however, it may be used to illuminate manyother apparatus as well, such as electronic devices, including cellulartelephones, calculators, PDAs, and so on.

Element 22 can be emitting light at a single wave length, oralternatively it may be adapted to emit at several wave lengths, forexample by providing several semiconductor junctions on the samesubstrate. In this latter configuration, additional wires may berequired-to provide appropriate excitation for the device.

FIG. 6 shows another embodiment of the invention wherein a plurality oflight emitting elements, such as 22A, 22B and 22C are provided on asubstrate 12′. Of course these elements may be distributed on thesubstrate 12′ in any desired pattern and may be used to produce staticor moving images on the substrate. Each of the elements may be connectedto conductors C which provide excitation to these elements. In thedrawings, the conductors C are shown as being formed in a radialpattern. However, the conductors may be arranged in any pattern.Moreover, two conductors C may be provided for each element, or some ofthe conductors may be shared, especially if more than one element isexcited at a time.

The elements are energized by connecting the conductors associatedtherewith to appropriate mechanical and/or electronic switches wellknown in the art.

The light emitting elements in the multi-colored configurations may beformed into groupings of a red, a blue and a green element so that whenproperly excited, the elements can be used to form colored images.

Obviously, numerous other modifications may be made to the inventionwithout departing from its scope as defined in the appended claims.

What is claimed is:
 1. A semiconductor illumination device for providing illuminating an object, comprising: a unitary substrate adapted to extend over the object; a plurality of conductors deposited on the substrate; and a light emitting element formed as a packageless semiconductor junction attached to said conductors and oriented on said substrate to direct radiation toward the object.
 2. The device of claim 1 wherein said substrate is transparent.
 3. The device of claim 1 wherein said substrate is opaque.
 4. The device of claim 1 wherein said light emitting element is adapted to generate multi-colored light.
 5. The device of claim 1 wherein said light emitting element is adapted to generate UV light.
 6. A semiconductor illumination device comprising: a transparent substrate; a plurality of conductors deposited on said substrate; a plurality of light emitting elements attached to said substrate and connected to said conductors to receive excitation signals, said light emitting elements being formed of packageless semiconductor junction.
 7. The device of claim 6 wherein each said light emitting element generates a different colored light.
 8. The device of claim 6 wherein said plurality of light emitting elements are packaged in a flip chip having a surface with connecting bumps, said connecting bumps being electrically connected to said conductors.
 9. The device of claim 6 wherein said conductors comprise several layers including a first layer made of a conductive material and a protective layer.
 10. The device of claim 6 conductors include several coextensive layers including a layer of Cr deposited on the substrate, a layer of Ni and a layer of Au.
 11. The device of claim 10 further comprising a protective layer formed on top of the other layers for protection.
 12. The device of claim 10 wherein said substrate is a glass.
 13. A semiconductor illumination device for illuminating an object comprising: a substrate arranged to disposed over said object; a plurality of conductors deposited on said substrate; and a light emitting element attached to said substrate and connected to said conductors to receive excitation signals, said light emitting element being formed of a packageless semiconductor junction.
 14. The device of claim 13 wherein said light emitting element is packaged in a flip chip having a surface with connecting bumps, said connecting bumps being electrically connected to said conductors.
 15. The device of claim 13 wherein said conductors comprise several layers including a first layer made of a conductive material and a protective layer.
 16. The device of claim 13 conductors include several coextensive layers including a layer of Cr deposited on the substrate, a layer of Ni and a layer of Au.
 17. The device of claim 13 further comprising a protective layer formed on top of the other layers for protection.
 18. The device of claim 16 wherein said substrate is a glass. 